[meteorite-list] Glass in meteorites

Wed Jun 25 00:24:28 EDT 2008

Hi,  Several years ago I ran onto an  unusual chondrule in JaH 055 that looks 
like glass but it is forming in  crystals.  I have had various explanations 
presented to me and all involved  "Glass"  This might be "On topic"?

If any one is up to taking a look  and sharing their observations, I would 
greatly appreciate it.   

Just go to my Meteorite Times Micrograph Gallery   
http://www.meteorite.com/meteorite-gallery/meteorites-alpha_frame.htm    and select alphabetical 
sorting, JaH 055, and then crystal  structure.

These shots were produced using incident (reflected  light).

Thanks,  Tom Phillips

In a message dated 6/24/2008  10:02:55 P.M. Mountain Daylight Time, 
cynapse at charter.net writes:
Have any  studies been done on "decay" of glasses in meteorites into  
crystaline
configurations?  Is there a mesurable rate, or does it not  happen?

This story brought that to mind-- if impact-generated glasses in  meteorites 
HAVE
NOT "decayed" into crystaline material in 4 billion years,  it's fairly good
evidence that it won't happen "in billions of years", as the  story  
speculates.

http://www.foxnews.com/story/0,2933,370864,00.html

Scientists  have made a breakthrough discovery in the bizarre properties of
glass, which  behaves at times like both a solid and a liquid.

The finding could lead  to aircraft that look like Wonder Woman's plane. Such
planes could have wings  of glass or something called metallic glass, rather 
than
being totally  invisible.

The breakthrough involved solving the decades-old problem of  just what glass 
is.

It has been known that that despite its solid  appearance, glass and gels are
actually in a "jammed" state of matter —  somewhere between liquid and solid —
that moves very slowly.

Like cars  in a traffic jam, atoms in a glass are in something like suspended
animation,  unable to reach their destination because the route is blocked by
their  neighbors.

So even though glass is a hard substance, it never quite  becomes a proper 
solid,
according to chemists and materials  scientists.

Work so far has concentrated on trying to understand the  traffic jam, but now
Paddy Royall from the University of Bristol in England,  with colleagues in
Canberra, Australia and Tokyo, has shown that glass fails  to be a solid due 
to
the special atomic structures that form in a glass when  it cools.

Icosahedron jams

Some materials crystallize as they  cool, arranging their atoms into a highly
regular pattern called a lattice,  Royall said, but although glass "wants" to 
be
a crystal, as it cools the  atoms become jammed in a nearly random 
arrangement,
preventing it from  forming a regular lattice.

In the 1950s, Sir Charles Frank in the Physics  Department at Bristol 
suggested
that the arrangement of the "jam" should form  what is known as an 
icosahedron,
but at the time he was unable to prove  it.

An icosahedron is like a 3-D pentagon, and just as you cannot tile a  floor 
with
pentagons, you cannot fill 3-D space with icosahedrons, Royall  explained. 
That
is, you can't make a lattice out of pentagons.

When it  comes to glass, Frank thought, there is a competition between  
crystal
formation and pentagons that prevents the construction of a  crystal.

If you cool a liquid down and it makes a lot of pentagons and  the pentagons
survive, the crystal cannot form.

It turns out that  Frank was right, Royall said, and his team proved  this
experimentally.

You can't watch what happens to atoms as they  cool because they are too 
small,
so Royall and his colleagues used special  particles called colloids that 
mimic
atoms, but are large enough to be  visible using state-of-the-art microscopy.

The team cooled some down and  watched what happened.

What they found was that the gel these particles  formed also "wants" to be a
crystal, but it fails to become one due to the  formation of icosahedra-like
structures — exactly as Frank had  predicted.

"It is the formation of these structures that underlie jammed  materials and
explains why a glass is a glass and not a liquid — or a solid,"  Royall said.

The findings are detailed in the June 22 issue of the  journal Nature 
Materials.
The research was supported in part by a grant from  Britain's Ministry of
Education, Culture, Sports, Science and Technology as  well as the Royal 
Society.

Preventing jetliner disasters

Knowing  the structure formed by atoms as a glass cools represents a  major
breakthrough in the understanding of meta-stable materials and will  allow
further development of new strong yet light materials called metallic  
glasses,
Royall said, which is already used to make some golf  clubs.

This stuff is generally shiny black in color, not transparent, due  to having 
a
lot of free electrons (think of mercury in an old  thermometer).

Metals normally crystallize when they cool, but stress  builds up along the
boundaries between crystals, which can lead to metal  failure.

For example, the world's first jetliner, the British built De  Havilland 
Comet,
fell out of the sky due to metal failure.

When metals  are be made to cool with the same internal structure as a glass 
and
without  crystal grain boundaries, they are less likely to fail, Royall  said.

Metallic glasses could be suitable for a whole range of products  beyond golf
clubs that need to be flexible such as aircraft wings and engine  parts, he 
said.

Glass is not what it seems

Royall is part of a  group of scientists who think that if you wait long 
enough,
perhaps billions  of years, all glass will eventually crystallize into a true
solid.

In  other words, glass is not in an equilibrium state, he believes, although  
it
appears that way to us during our limited lifetimes.

"This is not  universally accepted," Royall told LiveScience. "Our work will 
go
some way to  making that point more accepted. I think there is a growing 
weight
of  evidence that certainly many glasses 'want' to be a crystal."

Still,  glass "looks like a liquid and this is one of the great riddles that 
we
have  gone some way to solving," Royall said. "It has always been thought  
that
glass has same structure as a liquid, and that's why it looks like it.  It 
does
not have same structure as liquid."

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